Biotechnology and Its Applications: CBSE Class 12 Biology Chapter 10 Revision Notes

Biotechnology utilizes genetically modified organisms (GMOs)—including microbes, plants, and animals—to produce industrial-scale biopharmaceuticals and biologicals. Key applications span agriculture (pest-resistant crops), medicine (recombinant insulin and gene therapy), and research (transgenic disease models). The field focuses on providing the best biological catalysts, optimizing reaction conditions through engineering, and refining downstream processing for purification. While biotechnology offers solutions for food security and health, it necessitates strict oversight by bodies like the GEAC to address ethical concerns and prevent biopiracy.

1. Applications in Agriculture

Biotechnology aims to increase food production through genetically engineered crop-based agriculture as an alternative to agro-chemical or organic methods.

• Tissue Culture & Totipotency:
• Totipotency: The capacity of any plant cell or "explant" to generate a whole new plant under sterile conditions in nutrient media.
• Micro-propagation: Producing thousands of plants rapidly via tissue culture; these plants are somaclones (genetically identical to the parent).
• Somatic Hybridization: Fusing naked protoplasts from different varieties to create somatic hybrids (e.g., the "Pomato").
• Genetically Modified Organisms (GMO):
• Abiotic Stress Tolerance: Crops made resistant to cold, drought, salt, and heat.
• Nutritional Enhancement: Example: Golden Rice (enriched with Vitamin 'A').
• Reduced Post-harvest Losses: Improved shelf life and mineral usage efficiency.
• Pest Resistant Plants:
• Bt Cotton: Contains toxin genes from the bacterium Bacillus thuringiensis.
• Mechanism: The toxin exists as an inactive protoxin; once ingested, the alkaline pH of the insect gut solubilizes the crystals, activating the toxin.
• Effect: The activated toxin creates pores in the midgut epithelial cells, leading to swelling, lysis, and death.
• Specific Genes: cryIAc and cryIIAb control cotton bollworms; cryIAb controls corn borer.
• RNA Interference (RNAi): A cellular defense method in all eukaryotes where a specific mRNA is silenced by a complementary dsRNA molecule.
• Used to protect tobacco plants from the nematode Meloidegyne incognitia.

2. Applications in Medicine

Recombinant DNA technology allows for the mass production of safe, effective therapeutics that do not induce unwanted immunological responses.

• Genetically Engineered Insulin:
• Earlier insulin was extracted from slaughtered cattle and pigs, often causing allergies.
• Structure: Consists of two short polypeptide chains (Chain A and Chain B) linked by disulphide bridges.
• Eli Lilly (1983): Prepared DNA sequences for chains A and B, introduced them into E. coli plasmids, and combined the produced chains via disulphide bonds.

Comparison: Pro-insulin vs. Mature Insulin

Feature	Pro-insulin (Mammals)	Mature Functional Insulin
Components	Contains Chain A, Chain B, and C-peptide.	Contains only Chain A and Chain B.
Status	Inactive pro-hormone that requires processing.	Fully functional hormone.
Disulphide Bonds	Present between A and B chains.	Present between A and B chains.

• Gene Therapy:
• A method to correct gene defects diagnosed in children or embryos by inserting a functional gene to compensate for a non-functional one.
• ADA Deficiency: First clinical case (1990) in a 4-year-old girl.
• Treatment: Lymphocytes are cultured, a functional ADA cDNA is introduced using a retroviral vector, and cells are returned to the patient. Permanent cure involves introducing the gene at early embryonic stages.
• Molecular Diagnosis:
• PCR (Polymerase Chain Reaction): Detects very low concentrations of pathogens (like HIV) by amplifying their nucleic acids before symptoms appear.
• ELISA: Based on antigen-antibody interaction; detects pathogens via antigens or produced antibodies.
• Probes: Radioactive single-stranded DNA/RNA used to identify mutated genes through hybridisation and autoradiography.

3. Transgenic Animals

Animals with manipulated DNA to express foreign genes; 95% of these are mice.

• Normal Physiology: Studying gene regulation and growth factors (e.g., insulin-like growth factor).
• Disease Models: Animals designed to study cancer, cystic fibrosis, rheumatoid arthritis, and Alzheimer's.
• Biological Products: Rosie the cow (1997) produced milk enriched with human alpha-lactalbumin (2.4g/L), which is nutritionally superior for babies.
• Safety Testing: Using mice for polio vaccine safety and toxicity testing for drugs.

4. Ethical Issues and Biopiracy

• GEAC (Genetic Engineering Approval Committee): An Indian government body that evaluates the safety of GM research and public services.
• Biopiracy: The unauthorized use of bio-resources by multinational companies without proper compensation to the countries of origin.
• Basmati Rice Case: In 1997, a US company patented a "new" variety of Basmati derived from Indian farmer varieties, leading to legal and ethical disputes.

Frequently Asked Questions (FAQs)

1. Why does the Bt toxin not kill the Bacillus bacterium itself?
   
   The Bt toxin is produced as an inactive protoxin within the bacterium. It only becomes lethal when it enters an insect's gut, where the alkaline pH converts it into an active form.
   
   
2. What was the main challenge in producing human insulin using rDNA techniques?
   
   The primary challenge was getting the insulin to assemble into its mature form. In humans, insulin is produced as a pro-hormone containing an extra C-peptide that must be removed, a process Eli Lilly bypassed by producing and joining chains A and B separately.
   
   
3. How does RNA interference (RNAi) help in creating pest-resistant plants?
   
   RNAi silences a specific mRNA of a parasite by using a complementary dsRNA molecule that prevents translation. This prevents the parasite from surviving in the transgenic host, thereby protecting the plant from infestation.

Analogy for Understanding

Think of Gene Therapy like replacing a broken part in a factory assembly line. If a specific machine (the gene) is faulty, engineers (scientists) can either try to repair it temporarily (periodic infusions) or replace the machine entirely at the factory's foundation (embryonic stage) to ensure the assembly line runs perfectly forever.